Hi OP
As someone who works in this field I do agree that from what you’ve said your therapist behaved inappropriately.
I would never have agreed to the emails as it already feels like a boundary crossed, but, if I were then getting too many then in the next session I would apologise that I hadn’t managed to read them, discuss with you what’s helpful about me reading them to see if there was a way of it being more workable e.g. you pulling out the salient bits yourself after re-reading emails and just sending me a summary. If that was still too much I would ask that we don’t do the email thing and if there is a better way for you.
With the cancellation I would keep to the boundary that a cancellation before 24 hours still incurs a cost. If you requested a quick phone call instead I would probably say no because you can’t do proper therapy in a quick phone call (although it depends on the model you use).
If you sent me a cross message about that I would see it as my professional job to apologise for any upset caused. Listen to you carefully. Clarify any misunderstandings and discuss with you whether you want to continue or not and make some clearer boundaries/rules together.
If I felt overwhelmed by you I would seek supervision, try and figure out what that was about and try and work with you in our relationship on that.
If I felt I couldn’t work with you I would NEVER blame you but state that it’s my skills that are lacking. Therapists who are well trained, well supervised, have a clear model and support can work effectively with extremely challenging behaviour. If I couldn’t work with it would be because I didn’t have the right skills, the right support, the right model or the infrastructure (team of people for example) to do it.
Please don’t take this to heart and don’t let it put you off therapy. I don’t know all the details so can’t say for sure if what your therapist did wasn’t ok, but definitely don’t blame yourself. Talk it through with your next therapist and explain what happened and they will know to keep boundaries really clear and help you to think about the function of the long emails and a more effective way of using them.
By the time I’ve written this the post is likely to have moved on so apologies if it no longer makes sense!
Good luck OP - I hope there are smoother seas ahead for you 